In some great news for amputees and paralysis patients, monkeys have been able to control robotic limbs using only their thoughts, scientists report.

The animals were able to feed themselves using prosthetic arms, which were controlled only by brain activity.

Small probes, the width of a human hair, were inserted into the monkeys' primary motor cortex - the region of the brain that controls movement.With the probes inserted into the monkeys' motor cortices, computer software was used to interpret the brain's electrical impulses and translate them into movement through the robotic arm.After some training, two monkeys - who had had their own arms restrained - were able to use the prosthetic limbs to feed themselves with marshmallows and chunks of fruit.

The researchers said that the movements were fluid and natural.

The study shows that fewer than 100 tiny electrical signals generated in the specialised area known as the 'motor cortex' can command even complex arm and hand movements.

Writing in the journal Nature , they said their work could eventually help amputees and people who are paralysed.

The monkeys were able to use their brains to continuously change the speed and direction of the arm and the gripper, suggesting that the monkeys had come to regard the robotic arm as a part of their own bodies.

The success rate of the experiment was a very commendable 61%.

"The monkey learns by first observing the movement, which activates its brain cells as if it was doing it. It's a lot like sports training, where trainers have athletes first imagine that they are performing the movements they desire." said one of the scientists.

He said the research could eventually benefit the development of prosthetic limbs for people with spinal cord injuries or for amputees.

He said: "Our immediate goal is to make a prosthetic device for people with total paralysis."

"Ultimately, our goal is to better understand brain complexity."

"This moves the day when patients disabled after spinal cord injuries or amputations can use brain-controlled bionic limbs from the realm of science fiction towards science fact."

The more we understand about the brain, the better we'll be able to treat a wide range of brain disorders, everything from Parkinson's disease and paralysis to, eventually, Alzheimer's disease and perhaps even mental illness. --Dr Andrew Schwartz, University of Pittsburgh School of Medicine